Brake temperature detection device and electric parking brake control device

Abstract

A brake temperature detection device is configured detect brake temperature more accurately. In a situation in which the temperature in the vicinity of the brake has risen above the atmospheric temperature, indicated by a value read off of the detection signal of the temperature sensor, for example when traveling in congested traffic, a value to correct atmospheric temperature is determined, and atmospheric temperature is corrected on the basis of that atmospheric temperature correction value. Subsequently, brake temperature is calculated on the basis of the corrected air temperature. As a result of this configuration, it is possible to have the calculated brake temperature approach the actual brake temperature. This makes it possible to detect brake temperature more accurately.

The invention claimed is: 
     
       1. An electric parking brake control device for controlling an electric parking brake that drives a motor to generate a pressing force for pressing a friction material against a friction target material and generates a braking force by causing friction between the friction material and the friction target material, the electric parking brake control device comprising:
 lock control means that executes lock control by driving the motor to generate the pressing force and let the electric parking brake generate the braking force, stopping the drive of the motor to maintain the braking force to achieve a locked state when the braking force reaches a target braking force; and 
 a brake temperature calculation device that calculates a brake temperature in each control cycle, 
 said brake temperature calculation device including:
 means that calculates the amount of increase in brake temperature when a vehicle is braked; temperature rise judgment means that judges whether a temperature in a wheel house in the vehicle has risen above the atmospheric temperature indicated by the readings indicative of the calculation signal of a temperature sensor provided in the vehicle; 
 cooling temperature calculation means that calculates a brake cooling temperature in accordance with a difference between an atmospheric temperature indicated by a readings indicative of a calculation signal of the temperature sensor and a brake temperature calculated in the previous control cycle when the vehicle is not braked, the brake cooling temperature being a temperature of the brake cooled by natural cooling and corrects the atmospheric temperature by adding an atmospheric temperature correction value to the atmospheric temperature indicated by the readings indicative of the calculation signal of the temperature sensor, and uses the corrected atmospheric temperature to calculate the brake cooling temperature when the temperature rise judgment means judges that the temperature in the wheel house has risen above the atmospheric temperature indicated by the readings indicative of the calculation signal of the temperature sensor; and 
 brake temperature calculation means that calculates a brake temperature in the present control cycle by adding the amount of increase in brake temperature to the brake cooling temperature; and 
 
 wherein the lock control means sets a timing of ending the lock control or the control count of the lock control in accordance with the brake temperature calculated by the brake temperature calculation device. 
 
     
     
       2. The electric parking brake control device according to  claim 1 ,
 wherein when the temperature rise judgment means judges that the temperature in the wheel house has risen above the atmospheric temperature indicated by the readings indicative of the calculation signal of the temperature sensor, the cooling temperature calculation means corrects the brake cooling temperature by adding a brake temperature correction value to the brake cooling temperature, 
 wherein the brake temperature calculation means uses the corrected brake cooling temperature to calculate the brake temperature. 
 
     
     
       3. The electric parking brake control device according to  claim 2 , the temperature rise judgment means judges that the temperature in the wheel house has risen above the atmospheric temperature indicated by the readings indicative of the calculation signal of the temperature sensor when the vehicle is traveling in congested traffic, and corrects the atmospheric temperature to a value higher than the atmospheric temperature indicated by the readings indicative of the calculation signal of the temperature sensor. 
     
     
       4. The electric parking brake control device according to  claim 2 , further comprising traffic congestion level judgment means that judges a traffic congestion level indicating a degree of traffic congestion,
 wherein either or both of the atmospheric temperature correction value and the brake temperature correction value are set to be larger as the traffic congestion level is higher. 
 
     
     
       5. The electric parking brake control device according to  claim 4 , wherein the traffic congestion level judgment means has a plurality of low speed travel judgment threshold values each of which is a threshold value to be compared with a vehicle speed of the vehicle, and a plurality of low speed travel judgment times each of which is a threshold value to be compared with a continuation time in which the vehicle speed is equal to or less than the low speed travel judgment threshold value, and judges that the traffic congestion level is higher as the vehicle speed is equal to or less than the lower one among the low speed travel judgment threshold values or as the continuation time is equal to or more than the longer one among the low speed travel judgement times. 
     
     
       6. The electric parking brake control device according to  claim 4 , wherein the traffic congestion level judgment means has a plurality of braking loads during low speed travel each of which is a threshold value to be compared with a braking load represented by a braking initial speed being the vehicle speed at the start of braking and the number of brakings per predetermined distance, and a plurality of numbers of braking loads during low speed travel each of which is a threshold value to be compared with the number of braking loads equal to or less than the braking load during low speed travel, and judges that the traffic congestion level is higher as the braking load is equal to or less than the smaller one among the braking loads during low speed travel or as the number of braking loads equal to or less than the braking load during low speed travel is equal to or more than the larger one among the numbers of braking loads during low speed travel.